Effect of redox status on the metabolic characteristics and microbiota composition of high-amylose maize starch during in vitro fermentation

Redox status significantly shapes high-amylose maize starch fermentation patterns. • Redox elevation increases acetate proportion but reduces butyrate fraction. • Redox elevation selectively enriches facultative anaerobes and acetate producers. • Redox status reshapes microbial metabolic functions. We investigated the effects of continuous redox gradients (0–12% O 2 ) on the metabolic profiles of high-amylose maize starch (HAMS) in an in vitro human fecal fermentation system. After 24 h fermentation, total short-chain fatty acid production remained stable under mild oxidation (2% O 2 ). However, a clear metabolic shift occurred: acetate proportions increased from 25.70% to 32.55%, whereas butyrate declined from 16.19% to 9.88%. Under high oxidation (12% O 2 ), total fermentation was markedly suppressed (from 52.69 to 15.25 mmol/L), with metabolism shifting drastically toward acetate (69.09%) over butyrate (2.18%). This shift resulted from the selective enrichment of facultative anaerobes and acetate producers ( e.g. , Klebsiella and Parabacteroides ) and the depletion of strict anaerobic butyrate producers ( e.g. , Butyricicoccus ). Functional predictions revealed that oxidative stress redirected microbial metabolism from anaerobic fermentation to aerobic stress-response pathways. Overall, redox status critically shapes the HAMS fermentation profile, offering a theoretical foundation for redox-targeted dietary interventions with HAMS. Download: Download high-res image (208KB) Download: Download full-size image